1. Field of the Invention
The present invention relates to a method for controlling a participant-image camera or an original-image camera in a video conference system which enables a conference to be conducted between remotely located points.
2. Description of the Related Art
FIGS. 1 and 2 show one example of a general video conference system. FIG. 1 is a block diagram schematically showing the arrangement of a terminal apparatus, and FIG. 2 is a block diagram schematically showing the state in which terminal apparatuses, each of which is similar to that shown in FIG. 1, are installed in a conference room A and a conference room B, respectively. The conference room A serves as a station in which one conference participant himself is positioned (hereinafter referred to as "present station"), while the conference room B serves as a station in which another conference participant is positioned (hereinafter referred to as "remote station"), and the present station and the remote station are connected by a communication line.
In the terminal apparatus shown in FIG. 1, a participant-image camera 10 is provided for picking up an image of a conference participant. The participant-image camera 10 generally adopts an arrangement in which a camera part is disposed on a panhead part. The operation of the participant-image camera 10 in the direction of panning or tilting is controlled through remote control of the panhead part. A control circuit 11 performs control of the operations of the camera part of the participant-image camera 10, such as focusing, zooming and iris adjustment, or control of the panning or tilting operation of the panhead part. In FIG. 1, the participant-image camera 10 is shown as one block since the camera part and the panhead part are integrally assembled. However, it is also possible to adopt a participant-image camera of the type in which the camera part and the panhead part are separately provided.
An original-image camera 12 is provided for picking up an image of an original 16 placed on an original supporting base 14. A camera control circuit 18 is provided for controlling the operations of the original-image camera 12, such as focusing, zooming and iris adjustment. If the original-image camera 12 has a panhead function, the camera control circuit 18 also controls the panhead function. A monitor device 20 displays an image picked up by the participant-image camera 10 or the original-image camera 12, and also displays an image transmitted from a remote station. Although one monitor device is shown in FIG. 1, it is also possible to adopt a system provided with a plurality of monitor devices. An image control circuit 22 controls the transmission of an image picked up by the participant-image camera 10 or the original-image camera 12 and the display of such an image on the monitor device 20, as well as the display of a received image on the monitor device 20.
The arrangement shown in FIG. 1 also includes a microphone 24 for input of sound, a speaker 26 for output of sound, a sound control circuit 28 for controlling the transmission of an input sound supplied from the microphone 24 as well as the outputting of the input sound and a received sound signal to the speaker 26.
The shown arrangement also includes a communication control circuit 30 which is connected to a communication line for controlling the communication of images and sounds, a system control circuit 32 for controlling the entire system, and an operating device 34 having a keyboard, a digitizer or the like for inputting a predetermined instruction.
FIG. 2 is a block diagram schematically showing the state in which the terminal apparatuses, each of which is identical to that shown in FIG. 1, are respectively installed in the conference room A which serves as the present station and the conference room B which serves as the remote station, both terminal apparatus being connected by the communication line. In the illustration of the terminal apparatus installed in the conference room A which serves as the present station, individual blocks are denoted by reference numerals in which the characters "A" are respectively added after the corresponding reference numerals used in FIG. 1. In the illustration of the terminal apparatus installed in the conference room B which serves as the remote station, individual blocks are denoted by reference numerals in which the characters "B" are respectively added after the corresponding reference numerals used in FIG. 1.
In such a system, a person "a", who is in the conference room A serving as the present station, operates an operating device 34A to control a control circuit 11A, a camera control circuit 18A, an image control circuit 22A, a sound control circuit 28A, a communication control circuit 30A and other associated circuits. The person "a" also controls a control circuit 11B for a participant-image camera 10B provided in the remote station, so that a person "b" who is in the conference room B serving as the remote station can be displayed at an optimum location on a monitor device 20A. Similarly, the person "a" can also control a control circuit 18B for an original-image camera 12B provided in the remote station.
In the meantime, the person "b" operates an operating device 34B to control a control circuit 11B, a camera control circuit 18B, an image control circuit 22B, a sound control circuit 28B, a communication control circuit 30B and other associated circuits. The person "b" also controls the control circuit 11A for the participant-image camera 10A provided in the present station, so that the person "a" who is in the conference room A serving as the present station can be displayed at an optimum location on a monitor device 20B. Similarly, the person "b" can also control the control circuit 18A for the original-image camera 12A. Thus, the person "a" and the person "b" hold a video conference.
If a video conference is conducted by using the system shown in FIGS. 1 and 2, the participant-image camera 10 is operated in the following manner. If the person "a" controls the control circuit 11B, which is provided in the conference room B serving as the remote station, in order to display the person "b" at an optimum location on the monitor device 20A, or if, in a video conference held by a plurality of participants, the person "a" turns the participant-image camera 10B from a particular person to another person in the conference room B serving as the remote station and displays that person on the monitor device 20A, the motion of the participant-image camera 10B involves a time lag which corresponds to the required communication time or a delay which occurs in a power transmission system in the operating mechanism of the participant-image camera 10B. Such a time lag leads to the following problems.
(i) If the person "a" pans or tilts the participant-image camera 10B while viewing the monitor device 20A, a time lag occurs which corresponds to the required communication time or the delay occurring in the power transmission system. As a result, the person "a" moves the participant-image camera 10B by an excess amount corresponding to the time lag, so that a target person is displayed at a location which deviates from the optimum location on the monitor device 20A. If the person "a" moves the participant-image camera 10B in the opposite direction to correct the location at which the target person is displayed, the person "a" similarly moves the participant-image camera 10B by an excess amount in the opposite direction. Since it takes a long time to display the target person at the optimum location on the monitor device 20A, the person "a" has a remarkably uncomfortable sensation.
(ii) If the person "a" controls, while viewing the monitor 20A, the operation, such as focusing, zooming or iris adjustment, of the participant-image camera 10B provided in the remote station, it takes a long time to display an image controlled in an optimum state on the monitor device 20A.
(iii) If the person "a" controls not the participant-image camera 10B but the original-image camera 12B, similar problems occur.